Abstract: The influence of nitrogen loading and high temperature shock on ANAMMOX (anaerobic ammonium oxidation) process with a 3.2 L UASB (up-flow anaerobic sludge blanket) reactor was investigated. The results showed that the UASB-ANAMMOX reactor is not only appropriate for the treatment of low ammonia containing wastewater, but also suitable for that of mediate to high ammonia containing wastewater. The nitrite reductase is more likely subjected to the inhibition of dissolved oxygen. A instant high temperature may give a heavy shock on the running of the reactor; however, the shock may be relieved because of an intrinsic mechanism caused by the ANAMMOX microbes, which resulted in the resilience of the reactor to a steady state.